Field of the Invention
Embodiments disclosed herein generally relate to lampheads for use in thermal processing chambers.
Description of the Related Art
Rapid thermal processing (RTP) and epitaxial deposition (epi) systems are employed in semiconductor chip fabrication to create, chemically alter or etch surface structures on semiconductor wafers. RTP and epi systems typically depend upon an array of high-intensity incandescent lamps fit into a lamphead and directed at the substrate or wafer. The lamps are electrically powered and can be very quickly turned off and on and a substantial fraction of their radiation can be directed to the substrate. As a result, the wafer can be very quickly heated without substantially heating the chamber and can be nearly as quickly cooled once the power is removed from the lamps.
A number of infrared lamps are located in the lamphead. During processing, radiation from the lamps radiates through an upper window, light passageways and a lower window onto a rotating semiconductor substrate in the processing chamber. In this manner, the wafer is heated to a required processing temperature. The lamphead may include a number of light pipes to deliver radiation from tungsten-halogen lamps to the processing chamber. The lamps are divided into multiple zones, which are located in a radially symmetrical manner. Each zone is separately powered by a lamp driver that is, in turn, controlled by a multi-input, multi-output controller. The lamps are connected to the lamp drivers through a large wiring collar and heavy-duty electrical cabling.
While reflective surfaces are the norm for retaining and focusing thermal energy on the substrate, too many reflective surfaces will result in a slow chamber cooling. Slower chamber cooling leads to longer step change times and slower throughput numbers.
Thus, there is a need in the art for better control of cooldown after thermal processing.